| A mathematical model was developed describing the anaerobic digestion of cellulosic fibers by two bacterial populations, the acid formers and the methane formers in a series of biochemical reactions. In the first reaction, the polymeric material was hydrolyzed by extracellular enzymes secreted by the acid formers to yield soluble organics which were subsequently metabolized to form volatile fatty acids. In the second reaction, the volatile acids were converted to carbon dioxide and methane by the methanogenic bacteria. This investigation focused on the bio-kinetics of the former reaction, the hydrolysis-acidification reaction and verification of the model with experimental data.;The complete anaerobic digestion model was also used to predict the bio-gas capability in a given reactor configuration. Three such reactor configurations were analyzed, the single packed bed system, the parallel packed bed system and the series packed bed system. It was found that the series packed beds system preferentially retained the effluent constituents, bacterial cell mass, and hydrolytic enzymes and was thus able to achieve a higher cellulose degradation rate. This was reflected in a higher gas production rate of 0.3 ml of bio-gas/V/day as compared with 0.185 for the other two systems.;Based on these results, a fermentation system for converting agricultural crops into methane was developed. It consisted of a series of packed beds forming the hydrolysis-acidification stage which was in turn connected in series with a methane producing reactor. A small scale (10 acres) gas generating system was analyzed. From a preliminary economic analysis, annual total cost was estimated to be ;Bio-kinetic data were obtained by a series of batch tests with carboxymethylcellulose and cellulose powder as the polymeric substrate. Good correlations were obtained between the test data and the model predictions. From a series of model simulations, it was found the kinetic factors most sensitive to all the biological growth processes were the specific enzyme production rate and the enzyme molecular activity. Thus, it was concluded that cellulose hydrolysis is rate-limiting in the hydrolysis-acidification reaction. |
